Fix yamldocs outputing `[flags]` in usage output

A similar change was made in the CLI itself, but is not
inherited by the code that generates the YAML docs.

Before this patch is applied;

```
usage: docker container exec [OPTIONS] CONTAINER COMMAND [ARG...] [flags]
```

With this patch applied:

```
usage: docker container exec [OPTIONS] CONTAINER COMMAND [ARG...]
```

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/yaml/generate.go

@@ -22,6 +22,7 @@ func generateCliYaml(opts *options) error {
 	dockerCli := command.NewDockerCli(stdin, stdout, stderr, false, nil)
 	cmd := &cobra.Command{Use: "docker"}
 	commands.AddCommands(cmd, dockerCli)
+	disableFlagsInUseLine(cmd)
 	source := filepath.Join(opts.source, descriptionSourcePath)
 	if err := loadLongDescription(cmd, source); err != nil {
 		return err
@@ -31,6 +32,23 @@ func generateCliYaml(opts *options) error {
 	return GenYamlTree(cmd, opts.target)
 }
 
+func disableFlagsInUseLine(cmd *cobra.Command) {
+	visitAll(cmd, func(ccmd *cobra.Command) {
+		// do not add a `[flags]` to the end of the usage line.
+		ccmd.DisableFlagsInUseLine = true
+	})
+}
+
+// visitAll will traverse all commands from the root.
+// This is different from the VisitAll of cobra.Command where only parents
+// are checked.
+func visitAll(root *cobra.Command, fn func(*cobra.Command)) {
+	for _, cmd := range root.Commands() {
+		visitAll(cmd, fn)
+	}
+	fn(root)
+}
+
 func loadLongDescription(cmd *cobra.Command, path ...string) error {
 	for _, cmd := range cmd.Commands() {
 		if cmd.Name() == "" {